Pramila Patten, the special representative of the UN Secretary-General on sexual violence in conflict, said many of the atrocities committed by the troops "could be crimes against humanity."

The UN official made the remarks during a press briefing in the Bangladeshi capital, Dhaka, on Sunday, after visiting the southeastern district of Cox's Bazar, which is located near the border with Myanmar.

"I heard horrific stories of rape and gang rape, with many of the women and girls who died as a result of the rape," Patten said, adding, "My observations point to a pattern of widespread atrocities, including sexual violence against Rohingya women and girls who have been systematically targeted on account of their ethnicity and religion."

The sexual violence in Rakhine was "commanded, orchestrated and perpetrated by the armed forces of Myanmar," the special representative said.

"The forms of sexual violence we consistently heard about from survivors include gang rape by multiple soldiers, forced public nudity and humiliation and sexual slavery in military captivity."

"One survivor described being held in captivity by the Myanmar armed forces for 45 days, during which time she was repeatedly raped. Others still bore visible scars, bruises and bite marks attesting to their ordeal," Patten stated.

The UN official added that the sexual violence was a key reason behind the exodus of the Rohingya and occurred in the context of "collective persecution" of the minority.

"The widespread threat and use of sexual violence was clearly a driver and push factor for forced displacement on a massive scale and a calculated tool of terror aimed at the extermination and the removal of the Rohingya as a group."

Patten earlier met women and girls who were among thousands of Rohingya Muslims that have sought refuge in Bangladesh.

More than 600,000 Rohingya have fled the predominantly-Buddhist country of Myanmar to Bangladesh since August 25, when a crackdown on the Rohingya intensified in Rakhine. The government has been engaged in a campaign against the minority, which the UN and human rights groups have called “a textbook example of ethnic cleansing.”